1. Field of the Invention
The present invention relates to an electronic apparatus powered by a fuel cell that generates electric power through chemical reaction of oxygen and fuel such as hydrogen and methanol.
2. Description of the Related Art
Many electronic apparatuses are powered by chemical batteries and/or AC adaptors that convert AC electric power into DC electric power. FIG. 1 shows an electronic apparatus, for example, which is powered by both a chemical cell and an AC adaptor. By controlling a switch 14, a controller 16 selectively connects either a chemical cell 10 or an AC adaptor 12 to an electronic circuit 18. For example, when the chemical cell 10 is sufficiently charged, the chemical cell 10 is connected to the electronic circuit 18. When the chemical cell 10 is insufficiently charged, however, the AC adaptor 12 is connected to the electronic circuit 18 and provides electric power.
A fuel cell is well known as a device that generates electric power through the chemical reaction of fuel such as hydrogen and methanol, and oxygen (See a publication of unexamined Japanese Patent Application 9-213358 and a publication of examined Japanese Patent Application 6-54674, for example). Recent reduction in size of fuel cells has made it possible to use the fuel cells as power supplies for electronic apparatuses.
Since the energy density of the fuel cells is higher than that of chemical batteries, the use of the fuel cells extends battery life of the apparatuses. Additionally, the fuel cells continuously generate electric power as long as fuel such as methanol is provided, by consuming oxygen in the air. Battery re-chargers and AC adaptors become unnecessary.
Oxygen must be continuously provided to the fuel cells, however, so that the fuel cells can operate appropriately. If the oxygen density in the air provided to the fuel cells is lowered for any reason, the fuel cells cannot generate enough electric power to sustain the operation of the electronic apparatuses.
In the case that the fuel cells are used in a closed space, the oxygen density around the electronic apparatuses must be checked accordingly in order to ensure stable operation of the electronic apparatuses.
Accordingly, it is a general object of the present invention to provide a novel and useful electronic apparatus in which one or more of the problems described above are eliminated.
Another and more specific object of the present invention is to provide an electronic apparatus, powered by a fuel cell, which monitors oxygen density in the air provided to the fuel cell in order to control the operation mode of the electronic apparatus.
To achieve one of the objects of the present invention, an electronic apparatus includes an electronic circuit, a fuel cell that generates electric power by having fuel react with oxygen contained in the air and provides electric power to the electronic circuit, an oxygen density detector which detects oxygen density contained in the air provided to the fuel cell, and a controller which controls, in response to a first signal indicating the oxygen density sent by the oxygen density detector, power consumption of said electronic circuit.
The apparatus described above is further characterized in that the controller stores, in response to reception of the first signal sent by the oxygen density detector, the first signal therein, determines whether the first signal stored therein falls within one of a plurality of oxygen density ranges, and sends, if the first signal stored therein falls within one of the oxygen density ranges, a second signal to the electronic circuit, and that the electronic circuit having a plurality of power consumption modes each corresponding to one of the oxygen density ranges, reads, in response to reception of the second signal, the first signal stored in the controller, and selects one of the power consumption modes thereof.
The electronic apparatus according to the present invention controls its power consumption based on the oxygen density in the air provided to the fuel cell. In other words, the electronic apparatus can operate at its best performance in a certain oxygen density environment.
The first signal indicating the oxygen density is not necessarily the value of oxygen density, but any signal in connection with the oxygen density. Accordingly, the oxygen density can be measured at any position as long as the oxygen density is measurable, even in the exterior of the electronic apparatus. Further, the oxygen density can be calculated based on the output property of the fuel cell.
Other objects, features, and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.